From IMDB:

A high school teacher’s experiment to demonstrate to his students what life is like under a dictatorship spins horribly out of control when he forms a social unit with a life of its own.

From Netflix I could get the DVD for this German film whose German title is “Die Welle”. There are English subtitles available.

Jürgen Vogel, who plays the teacher Rainer Wenger, is well-known in Germany. Rainer must lead a classroom of students through a project called “Autocracy”.  He begins innocently to have the students experiment with disciplined unity: they decide to all wear white shirts to school instead of sloppy casual clothing; they adopt a hand signal that mimics a wave in the ocean; they create a logo for the group which they then stencil all over the town, to the point of vandalism; they militate against anyone who is not in the group. Finally the project snowballs out of control with some disastrous results.

In our current sad era of Donald Trumpet, the film teaches a worthwhile lesson in the rise of Fascism.